Flap devices of the above type are known in particular as throttle flaps for controlling the air supply to the internal combustion engine. In the process, the flap will be rotated in the duct housing, whereby the available flow cross section will be changed. Other applications for control of a gas flow, particularly of an air or exhaust gas flow, are also, however, known.
Various types of supports and designs of these flaps have been disclosed. In most cases, such flaps, which can be produced from plastic or metal, comprise a throughgoing shaft which is supported on both sides of the flap body in the duct housing. Primarily rolling bearings and, in this case, ball bearings are used for support. While the first shaft end is mostly supported in a blind hole of the duct housing, the opposite end passes through the duct housing. On this shaft end, a toothed wheel of a transmission is normally supported via which a connection to an electric motor is established, the electric motor serving as an actuator to drive the flap body and being connected to the control unit of the internal combustion engine.
Such a throttle body is described, for example, in DE 10 2007 013 937 A1. The rotary shaft, connected to the electric motor via the transmission, is supported in the duct housing by means of two needle bearings which include sealing rings.
DE 44 23 370 A1 describes a throttle flap made of plastic which comprises two opposite receiving openings for two shaft ends which are held in the openings in a form-locking manner. The flap body comprises rotary-bearing sites which are surrounded by a soft plastic sealing. DE 44 23 370 A1 does not disclose how the bearing support in the stub is actually realized.
The known designs have the disadvantage that the assembly process is relatively bothersome and that a high dimensional accuracy or additional measures are required in order the provide an exact position of the flap body when mounting the flap body in the duct in the direction of the axis of rotation. These designs are further vulnerable towards corrosive condensates.